HR: 08:15h
AN: SM21B-02    [Abstracts]
TI: Plasma Transport Along Discrete Auroral Arcs
AU: * Kullen, A
EM: kullen@irfu.se
AF: IRF Uppsala, Box 537, Uppsala, SE-75121, Sweden
AU: Buchert, S
EM: scb@irfu.se
AF: IRF Uppsala, Box 537, Uppsala, SE-75121, Sweden
AU: Lileo, S
EM: sonia.lileo@ee.kth.se
AF: Alfven Laboratory, KTH, Teknikringen 31, Stockholm, SE-10044, Sweden
AU: Johansson, T
EM: tommy.johansson@ee.kth.se
AF: Alfven Laboratory, KTH, Teknikringen 31, Stockholm, SE-10044, Sweden
AB: We study with help of strong E-field events the contribution of discrete auroral arcs to the total plasma flux in the high-latitude ionosphere. Common features of such arcs are a field-aligned potential drop and strong perpendicular E-field above. Due to parallel E-fields, the region above the acceleration region is partly decoupled from the ionosphere and strong, local plasma flows along the auroral arc are the consequence. As these plasma flows are directed in opposite directions on the different sides of the arc, a net plasma transport occurs only when the connected E-field is monopolar or the arc is located at a steep density gradient. For this case, it is proposed that the locally enhanced plasma convection helps to remove stresses in the magnetosphere that have built up due to friction in the ionosphere. 32 strong E-field events found in Cluster data are used. They all appear in the boundary region between polar cap and central plasma sheet. Most events appear during substorm expansion or recovery. For a large majority of the E-field events, a net plasma flux occurs. The plasma transport connected to strong E-field peaks is in two third of the cases in the same direction as the background flow within the boundary region. In one third of the cases the contribution of the E-peak is high enough to enhance the plasma flux in the boundary region considerably. Interestingly, in most expansion cases the E-peak related and background plasma transport in the boundary region is sunward, in most recovery cases the average plasma transport has an anti-sunward direction.
DE: 2407 Auroral ionosphere (2704)
DE: 2411 Electric fields (2712)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2437 Ionospheric dynamics
DE: 2463 Plasma convection (2760)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting